What happened
During the landing roll, the Stinson 108 began an uncontrolled left turn. The pilot attempted to counter the turn by applying opposite rudder, but the maneuver was unsuccessful. The aircraft subsequently departed the runway and struck a ditch, which caused the airplane to nose over and come to rest in an inverted position.
The investigation
An examination of the wreckage focused on the tailwheel assembly. Investigators found that the tailwheel spring clips had disconnected from the tailwheel springs; these components were noted to be stretched and distorted. The investigation revealed that approximately two weeks prior to the accident, the owner had installed a new tailwheel. During this installation, the owner chose not to use the new spring clips provided in the kit, opting instead to reuse the existing clips from the aircraft. It was determined that the owner was not a certificated mechanic and did not consult a professional mechanic during the installation process.
Findings
Findings indicated that the tailwheel spring clips had failed due to being reused rather than using the new hardware provided with the kit.